P335: PROGNOSTIC UTILITY OF NON-HOMOLOGOUS END JOINING DNA REPAIR PATHWAY GENES IN T-CELL ACUTE LYMPHOBLASTIC LEUKEMIA
Authors: Anita Chopra, Sarita Kumari, Mohit Arora, Avanish Pandey, Neha Thukral, Mercilena Benjamin, Jay Singh, Sameer Bakhshi, Atul Sharma, Jayanth Kumar, Pranay Tanwar
Journal: HemaSphere (2023)

Topic: 2. Acute lymphoblastic leukemia - Clinical Background: T-cell acute lymphoblastic leukemia (T-ALL) is a molecularly heterogeneous malignancy characterized by transformation and differentiation blockage at different stages of T cell development. Recent research has highlighted the critical role of different DNA repair pathways in ALL pathophysiology and drug resistance. However, more detailed studies are needed to determine the clinical significance of the major DNA double-strand break repair pathway, Non-Homologous End Joining (NHEJ), in T-cell acute lymphoblastic leukemia. Aims: To assess the relevance of DNA damage response pathways in T-ALL Methods: We assessed the expression pattern of 17 genes involved in NHEJ pathway including core genes, accessory genes and end processing enzymes in 244 T-ALL patients. Taqman probe chemistry based multiplex real time PCR reaction was utilized to amplify these genes. Effect of pharmacological inhibition of NHEJ pathway on T-ALL cell survival and its sensitization towards chemotherapy was assessed using MTS assay. Cells were treated with the NHEJ inhibitors and their effect on cellular processes including cell apoptosis and cell cycle were assessed. Results: The expression of core NHEJ pathway genes, including XRCC6, XRCC5, PRKDC, XRCC4, LIG4, and NHEJ1 and accessory genes, PAXX, APLF, and WRN, showed considerable overexpression compared to the controls. In addition, the genes involved in DNA damage correction, PNKP1, APTX, TDP1 and TDP2, polymerase including POLM, and nucleases including DCLRE1C and SETMAR exhibited higher expression in T-ALL patients. POLL gene exhibited no difference between T-ALL and controls. Coexpression analysis revealed that many of the genes involved in NHEJ pathway exhibited a strong positive correlation withs each other. On comparing the expression pattern among immunophenotypes, analysis revealed that many of these genes were upregulated in the immature subtype of T-ALL compared to other subtypes, including cortical and mature T-ALL. Survival analysis revealed that higher expression of most NHEJ pathway genes was associated with the worse patient’s survival. The use of inhibitors targeting the non-homologous end joining (NHEJ) pathway, specifically the PRKDC inhibitor NU7026 and the LIG4 inhibitor SCR7, sensitized Jurkat and MOLT4 T-cell acute lymphoblastic leukemia (T-ALL) cells to chemotherapeutic drugs such as prednisolone, daunorubicin, and etoposide. Summary/Conclusion: Our study has identified a unique expression profile of non-homologous end joining (NHEJ) genes in distinct immunophenotypic subgroups of T-cell acute lymphoblastic leukemia (T-ALL) patients, which may underlie differences in DNA repair capacity among patients with different immunological profiles and in response to therapy. Our findings suggest that inhibition of the NHEJ pathway could be a promising therapeutic approach to overcome therapy resistance in T-ALL. Keywords: ALL